1. Field of the Invention
This invention relates to a novel copolymer of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid (PIPE copolymer) as well as a manufacturing process therefor and a solution containing thereof. In particular, it provides a copolymer of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid useful as, for example, a base polymer in a positive photosensitive composition used for, e.g., manufacturing a color filter; relates to a process for manufacturing the copolymer from industrially available 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid; and provides a solution comprising the copolymer containing particular concentrations of remaining monomer components.
Furthermore, the copolymer of this invention is useful as a metal finishing agent for protecting a metal surface and improving corrosion resistance and paint-adhesion property of the metal surface.
2. Description of the Related Art
Recently, a color filter has been extensively used for a variety of multicolored liquid-crystal color displays such as a liquid-crystal color television. Such a color filter has been conventionally manufactured by, for example, screen printing and electrodeposition. However, as a color display has been improved for its resolution, it has been more important to refine a pattern. Thus, a variety of patterning processes utilizing photolithography have been investigated.
For example, JP-A 8-94827 discloses a process for manufacturing a color filter comprising the steps of (1) forming a transparent conductive layer on a transparent substrate; (2) forming a positive photosensitive coating layer; (3) exposing a part of the transparent conductive layer; (4) forming a colored area by electrodeposition; and (5) repeating steps (3) and (4) as required. Of these steps, a pattern refinement level depends on steps (2) and (3), in which photolithography is used. In particular, it significantly depends on a positive photosensitive composition applied on the transparent conductive layer. The above invention employs a positive photosensitive composition essentially comprising (a) a polymer containing both carboxyl and hydroxyphenyl groups in one molecule, (b) a compound containing two or more vinyl ether groups in one molecule, and (c) a compound generating an acid by irradiating an active energy beam.
This photosensitive composition is developed as follows; by heating the film on which the positive photosensitive composition has been applied, an addition reaction of the carboxyl group and/or hydroxyphenyl group with the vinyl ether group forms a crosslink, which is insoluble to a solvent or an alkali developing solution, and then, after irradiating with an active energy beam and then, as necessary, heating the film, an acid generated in the irradiated area acts as a catalyst to break the crosslink structure and thus to again make the irradiated area soluble to a solvent or an alkali developing solution. For further improving a resolution, a preferable polymer (base polymer) in a positive photosensitive composition is one containing both carboxyl and hydroxyphenyl groups in one molecule which meets all the following five requirements as much as possible;
(a) a higher solubility to a solution which solves a crosslinking agent, an acid-generating agent and others (solvent solubility);
(b) a certain dissolution rate of the broken crosslink moieties in an alkali developing solution after exposure (dissolution rate in an alkali developing solution);
(c) good diffusivity of an acid generated by irradiation with an active energy beam (acid diffusivity);
(d) transparency of a photosensitive coating at an exposure wavelength (transparency); and
(e) thermal stability during the heating step after application of the film and exposure (thermal stability).
As an example of a polymer meeting these requirements to some degree, a copolymer from p-hydroxystyrene, n-butyl. acrylate and acrylic acid has been disclosed in, for example, JP-A 8-94827 and 8-94829. We have, however, investigated the copolymer for its performance and have come to a conclusion that it is insufficiently soluble in a solvent or thermally stable.
A main starting material, p-hydroxystyrene, for the copolymer may be prepared by any of conventional processes; for example, (a) reacting p-tert-butoxyphenyl halide with metal magnesium to form p-tert-butoxyphenylmagnesium halide, which is then reacted with vinyl halide in the presence of a nickel-phosphine complex catalyst to form p-tert-butoxystyrene (JP-A 1-106835), and then breaking the tert-butoxy group with, for example, an acid to provide p-hydroxystyrene; and (b) converting p-halogenophenol via Grignard reaction into p-(t-butoxy)phenylmagnesium halide, which is then reacted with tri-n-alkyl borate, hydrolyzing a resulting reaction product, and treating a product with hydrogen peroxide to provide p-hydroxystyrene (JP-A 62-39536).
For both processes, there are many problems; for example, the process consists of complex multiple stages, metal components such as magnesium and nickel must be removed from a product, and using magnesium halide leads to a large amount of metal halide, a byproduct, which requires complicated treatment. In the process described in (a), an expensive complex containing phosphine ligand is used as a catalyst, and therefore, recovery and recycle of the catalyst is indispensable, which makes the process more complicated. In the process described in (b), a large amount of tri-n-alkyl borate must be used, which makes separation of the product from the borate and treatment of the borate more complicated. Thus, p-hydroxystyrene cannot be said to be an industrially available starting material. A copolymer from the compound has not, therefore, been used as a base polymer for a positive photosensitive composition.
On the other hand, 4-(1-methylethenyl)phenol can be readily prepared by thermal decomposition of 2,2-bis(4xe2x80x2-oxyphenyl)propane (hereinafter, referred to as xe2x80x9cbisphenol Axe2x80x9d (a popular name)) (e.g., JP-B 56-52886). Therefore, industrially available 4-(1-methylethenyl)-phenol has been paid attention. Furthermore, it is expected that the compound has considerably different properties such as higher thermal stability or acid-diffusivity and modified solubility because of effects of its xcex1-methyl-group. A copolymer prepared using 4-(1-methylethenyl)phenol as a monomer has been intensely investigated for a variety of applications.
For example, JP-As 6-289608 and 9-292709 disclose binary copolymers of 4-(1-methylethenyl)phenol and tert-alkyl acrylate as an example of a polymer for a radiosensitive (resist) composition. On irradiating an active energy beam, these copolymers change solubility in their irradiated part due to an acid derived from a compound capable of generating an acid by an active beam, and then may act as a positive resist by using an alkali developing solution. Thus, the technique utilizes instability of a tert-alkyl ester group to an acid. Such a copolymer, however, has an insufficient dissolution rate in an alkali developing solution and insufficient acid diffusivity, and is poorly reactive to a vinyl ether compound as a crosslinking agent. It cannot be, therefore, used as it is.
JP-A 61-293249 discloses a binary copolymer of 4-(1-methylethenyl)phenol and n-butyl acrylate as an example of a copolymer for a resin composition exhibiting damping property. The copolymer has an extremely lower dissolution rate in an alkali developing solution and is poorly compatible with a vinyl ether compound. It cannot be, therefore, used as it is.
On the other hand, a variety of techniques have been developed, in which a metal surface is chemically treated to form a non-metallic film over the metal for improving surfacequality. For example, JP-As 59-207971, 59-207972, 1-172406 and 1-177380 disclose that derivatives of poly-4-vinylphenol are useful as such a metal finishing agent. These metal finishing agents, however, exhibit corrosion. resistance or paint adhesion property insufficient to be practically used.
An objective of this invention is to provide a copolymer comprising industrially available 4-(1-methylethenyl)phenol as a structural unit and useful as a positive photosensitive composition for manufacturing a color filter, as well as a convenient process for manufacturing the copolymer.
Another objective of this invention is to provide a copolymer exhibiting improved corrosion resistance and paint adhesion property as a metal finishing agent, and a convenient process for manufacturing the copolymer.
To achieve the above objectives, we have prepared a variety of copolymers using 4-(1-methylethenyl)phenol and different monomers, to investigate them for their relationship between their basic physical properties and structures, and then have surprisingly found that a copolymer prepared from 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid as structural units in a particular composition ratio can meet all the above five requirements ((a) solvent solubility, (b) dissolution rate in an alkali developing solution, (c) acid diffusivity, (d) transparency and (e) thermal stability).
Furthermore, we have investigated effects of different compounds in a polymerization solution after copolymerizing 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid as well as of the composition and the molecular weight of the copolymer, on resist properties. Then, we have surprisingly found that a polymerization solution prepared by a particular process, containing the copolymer having a particular composition in a particular amount and containing a certain amount of remaining monomers can provide a copolymer which can meet all the above five requirements ((a) solvent solubility, (b) dissolution rate in an alkali developing solution, (c) acid diffusivity, (d) transparency and (e) thermal stability).
We have used the copolymer as an additive for a metal finishing agent, and have surprisingly found that it can achieve higher corrosion resistance and paint adhesion property than any conventional agent.
Thus, this invention provides;
(I) a copolymer comprising structural units represented by formula (1): 
formula (2): 
where R1 is hydrogen or methyl and R2is C1-C6 straight or branched unsubstituted alkyl or C1-C6 straight or branched substituted alkyl, and formula (3): 
where R3 is hydrogen or methyl,
wherein the mole fractions, a, b and c, are 0.05 to 0.7, 0.15 to 0.8 and 0.01 to 0.5, respectively and a+b+c=1;
(II) a copolymer described in (I) where a, b and c are 0.10 to 0.45, 0.30 to 0.8 and 0.05 to 0.30, respectively and a+b+c=1;
(III) a copolymer described in (I) where a, b and c are 0.10 to 0.30, 0.50 to 0.8 and 0.05 to 0.20, respectively and a+b+c=1;
(IV) a copolymer described in any of (I) to (III) where R2 in the structural unit represented by formula (2) is C1-C6 straight or branched unsubstituted primary or secondary alkyl or C1-C6 straight or branched hydroxylated primary or secondary alkyl;
(V) a copolymer described in any of (I) to (III) where R2 in the structural unit represented by formula (2) is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and 2-hydroxyethyl;
(VI) a copolymer described in any of (I) to (III) whose weight-average molecular weight and molecular-weight dispersion are 3,000 to 50,000 and 1.0 to 3.0, respectively;
(VII) a copolymer described in any of (I) to (III) whose glass transition point is 30 to 150xc2x0 C.;
(VIII) a copolymer described in any of (I) to (III) whose transmittance at 350 nm is at least 90%/xcexcm;
(IX) a copolymer described in any of (I) to (III) whose dissolution rate in a 2.38 wt % aqueous solution of tetramethylammonium hydroxide is at least 1 xcexcm/min.;
(X) a process for manufacturing a copolymer described in (I), comprising heating a mixture of (a) 4-(1-methylethenyl)phenol, (b) a (meth)acrylate represented by formula (4): 
where R1 is hydrogen or methyl and R2 is C1-C6 straight or branched unsubstituted alkyl or C1-C6 straight or branched substituted alkyl, (c) a (meth)acrylic acid represented-by formula (5): 
where R3 is hydrogen or methyl, (d) a radical-polymerization initiator, and (e) a solvent, in which the mole fractions of 4-(1-methylethenyl)phenol (a), the (meth)acrylate (b) and the (meth)acrylic acid (c) are 0.05 to 0.7, 0.15 to 0.8 and 0.01 to 0.5, respectively and the total of the mole fractions is 1;
(XI) a process for manufacturing a copolymer described in (II), comprising heating a mixture of (a) 4-(1-methylethenyl)phenol, (b) a (meth)acrylate represented by formula (4), (c) a (meth)acrylic acid represented by formula (5), (d) a radical-polymerization initiator, and (e) a solvent, in which the mole fractions of 4-(1-methylethenyl)phenol (a), the (meth)acrylate (b) and the (meth)acrylic acid (c) are 0.10 to 0.45, 0.30 to 0.8 and 0.05 to 0.30, respectively and the total of the mole fractions is 1;
(XII) a process for manufacturing a copolymer described in (III), comprising heating a mixture of (a) 4-(1-methylethenyl)phenol, (b) a (meth)acrylate represented by formula (4), (c) a (meth)acrylic acid represented by formula (5), (d) a radical-polymerization initiator, and (e) a solvent, in which the mole fractions of 4-(1-methylethenyl)phenol (a), the (meth)acrylate (b) and the (meth)acrylic acid (c) are 0.10 to 0.30, 0.50 to 0.8 and 0.05 to 0.20, respectively and the total of the mole fractions is 1;
(XIII) a process described in any of (X) to (XII) heating the materials while continuously or intermittently supplying 4-(1-methylethenyl)phenol (a), the (meth)acrylate (b) and/or the (meth)acrylic acid (c) into the reaction system to maintain the total concentration of (a), (b) and (c) in the reaction system at 20 wt % or lower throughout the heating step;
(XIV) a process described in any of (X) to (XII) where the (meth)acrylate represented by formula (4) is selected from the group consisting of unsubstituted primary or secondary alkyl acrylate, hydroxylated primary or secondary alkyl acrylate, unsubstituted primary or secondary alkyl methacrylate, and hydroxylated primary or secondary alkyl methacrylate;
(XV) a process described in (XIV) where the (meth)acrylate represented by formula (4) is selected from the group consisting of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate and 2-hydroxyethyl methacrylate;
(XVI) a process described in any of (X) to (XII) where the radical-polymerization initiator is selected from the group consisting of azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexane-carbonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, peroxylauroyl, peroxydiisopropyl dicarbonate and acetyl peroxide;
(XVII) a process described in any of (X) to (XII) where the materials are heated at 50 to 180xc2x0 C.;
(XVIII) a solution containing 25 to 75 wt % of a copolymer described in (I) prepared by heating a mixture of (a) 4-(1-methylethenyl)phenol, (b) a (meth)acrylate represented by formula (4), (c) a (meth)acrylic acid represented by formula (5), (d) a radical-polymerization initiator, and (e) a resist solvent, in which the mole fractions of (a), (b) and (c) are 0.05 to 0.7, 0.15 to 0.8 and 0.01 to 0.5, respectively and the total of the mole fractions is 1, and then optionally concentrating or diluting the mixture to adjust the concentrations of (a), (b) and (c) in the whole solution to 50 ppb to 0.5 wt %, 5 ppm to 5 wt % and 200 ppb to 2 wt %, respectively;
(XIX) a solution described in (XVIII) containing 25 to 75 wt % of a copolymer described in (II), where the mole fractions of (a), (b) and (c) are 0.10 to 0.45, 0.30 to 0.8 and 0.05 to 0.30, respectively and the total of the mole fractions is 1, and the concentrations of (a), (b) and (c) in the whole solution are adjusted to 50 ppb to 0.5 wt %, 5 ppm to 5 wt % and 200 ppb to 2 wt %, respectively;
(XX) a solution described in (XVIII) containing 25 to 75 wt % of a copolymer described in (III), where the mole fractions of (a), (b) and (c) are 0.10 to 0.30, 0.50 to 0.8 and 0.05 to 0.20, respectively and the total of the mole fractions is 1, and the concentrations of (a), (b) and (c) in the whole solution are adjusted to 50 ppb to 0.5 wt %, 5 ppm to 5 wt % and 200 ppb to 2 wt %, respectively;
(XXI) a solution described in any of (XVIII) to (XX) where the (meth)acrylate represented by formula (4) is selected from the group consisting of unsubstituted, primary or secondary alkyl acrylate, hydroxylated primary or secondary alkyl acrylate, unsubstituted primary or secondary alkyl methacrylate, and hydroxylated primary or secondary alkyl methacrylate;
(XXII) a solution described in (XXI) where the (meth)acrylate represented by formula (4) is selected from the group consisting of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate,. isobutyl methacrylate, sec-butyl methacrylate and 2-hydroxyethyl methacrylate;
(XXIII) a solution described in any of (XVIII) to (XX) where the radical-polymerization initiator is selected from the group consisting of azobisisobutyro-nitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tert-butyl peroxide, peroxylauroyl, peroxydiisopropyl dicarbonate and acetyl peroxide;
(XXIV) asolution described in any of (XVIII) to (XX) where the resist solvent is selected from the group consisting of ketones, alcohols, polyols, polyol derivatives, cyclic ethers and esters;
(XXV) a solution described in any of (XVIII) to (XX) where throughout heating, (a) 4-(1-methylethenyl)phenol, (b) a (meth)acrylate and/or (c) a (meth)acrylic acid are continuously or intermittently supplied to maintain the total concentration of (a), (b) and (c) at 20 wt % or lower;
(XXVI) a solution described in any of (XVIII) to (XX) where the materials are heated at 50 to 180xc2x0 C.;
(XXVII) a solution described in any of (XVIII) to (XX) where the concentrations of (a), (b) and (c) in the whole solution are 100 ppb to 0.1 wt %, 10 ppm to 3 wt %, and 500 ppb to 1 wt %., respectively;
(XXVIII) a solution described in any of (XVIII) to (XX) where the film formed by applying the solution on a substrate and then heating the substrate has a dissolution rate in a 2.38 wt % aqueous solution of tetramethylammonium hydroxide is at least 1 xcexcm/min;
(XXIX) a solution described in any of (XVIII) to (XX) where the film formed by applying the solution on a quartz substrate and then heating the substrate has a transmittance of at least 90%/xcexcm at 350 nm.
According to this invention, there can be provided a copolymer of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid, which is useful as, for example, a base polymer for a positive photosensitive composition used in, for example, manufacturing a color filter.
The copolymer may be readily prepared by radical polymerization of 4-(1-methylethenyl)phenol, a (meth)acrylate and a (meth)acrylic acid in particular charging conditions.
Furthermore, the copolymer exhibits improved corrosion resistance and paint-adhesion property as a metal finishing agent.